a) Field of the Invention
The present invention relates to an electrostatic dissipation device, and more particularly to an electrostatic dissipation device with static sensing and method thereof.
b) Description of the Related Art
The demand of semiconductor products steadily increases, and consumers turn to look for lighter, thinner, shorter and smaller electronic products. In addition, the feature size of electronic parts is continually minimized, and following the improvement of the semiconductor package, technological breakthrough is developed to comply with the demand of the electronic products markets.
Moreover, the manufacturing costs and added value of semiconductor products are high, and product performance is critical in determining the function of electronic goods. Therefore, each phase of the semiconductor manufacturing process, as well as each semiconductor chip, are undergone through numerous tests and examinations to assure the quality of final electronic products.
In general, testing process of the semiconductor product means the communication and appearance testing of the packaged chip, including like material preparation, tester testing, electrical testing, label scanning, automatic or manual foot selecting, foot testing and fixing, packaging, and so on, in which, the handler in the tester testing is used to determine whether the semiconductor product under test is ruined during the processes or is damaged by static. Static arises from ion movements between contact and separation of objects which causes an object to carry positive or negative charges. Semiconductor products in small size are easily pierced, burned or damaged by electrostatic discharge to be ineffective. Therefore, how to prevent static is an important issue for semiconductor manufacturers to address.
Most of semiconductor manufacturing processes are performed in the clean room, wherein the lower relative humidity tends to accumulate static, so the existence of static is unavoidable. The current electrostatic protection includes such as anti-static wrist straps, anti-static shoes, anti-static blower and anti-static bar. In the semiconductor manufacturing processes, semiconductor chips are automatically or manually shifted from a semiconductor carrier (like semiconductor tray) to a present tester by operators, after those semiconductor products under test are completed with testing one by one, they are shifted from the present testing machine to semiconductor tray. Different testing processes are performed by different machines, so the semiconductor products are necessary to be shifted to different machines for next test. In the shifting, if any electrostatic contamination occurs because of ineffective electrostatic protection resulted from operators' personal ignorance or equipment problem, the semiconductor chips undergone tens or hundreds of processes are ruined at once.
Please refer to FIG. 1, which concerns Taiwan Invention Patent No. 1435659, entitled “A static eliminator”, which is applicable to eliminate static of work piece. The static eliminator 1 is disposed on the bottom side of the long and slender box 1a, and plural, here means eight, main discharge electrode units 2 and four additional discharge electrode units 3 are partitioned and disposed on the long side. Furthermore, the four additional discharge electrode units 3 are optional to assemble based upon the users' choice, and the basic structure of the additional discharge electrode unit 3 and the main discharge electrode unit 2 are similar.
The method of pulse width modulation (PWM) is adopted by the static eliminator 1, by which the main discharge electrode unit 2 and the additional discharge electrode unit 3 are driven to discharge positive or negative ions, so that the electrostatic charges of work piece can be eliminated.
From the above descriptions, certain problems still exist in the prior art device:
1. Energy Wasting
In old times, the positive and negative ions are continually released for eliminating static, no matter whether any work piece exists on the testing zone, the ions are still continually generated by the static eliminator in high voltage, even though electrostatic balance is obtained, the equivalent positive and negative ions are released by the static eliminator to cause energy wasting.
2. Inadequate Electrostatic Elimination
The blowholes are disposed at intervals on the discharge needle in the prior art device, although it can prevent the needle tip from being damaged by accumulated impurities, inadequate ion dispersion is resulted from the blowholes, and even though the additional discharge electrodes are disposed on the main discharge electrodes, the ion dispersion state cannot be changed.
3. Reducing the Life Span
High voltage is generated by the static eliminator via the electronic circuit, and ions are generated from the discharge needle, the life span of the circuit and the needle has its limitation, when the electrostatic balance is detected, ions are still continuously generated to reduce the life span.
Because static will not disappear automatically, as long as static exists, it causes damages which can lead to a loss of millions or even ten millions of dollars. To enhance the reliability of products and to prevent from the electrostatic damage, the method and equipment of electrostatic dissipation in present testing processes are desirable to be improved.